This invention relates to a video display method for a video display device having a liquid crystal display, and in particular, to a video display method for a television using video signals produced by the interlace method in which the display is divided into an even field and an odd field during transfer of the video signals.
Conventional video display apparatus utilizing a liquid crystal display are small in size. In the conventional liquid crystal display, such as a liquid crystal television, video signals are transferred so that video signals of two adjacent scanning lines within a video field are divided into an even portion and an odd portion. Both portions are displayed on the same line of the television display due to the small size of the liquid crystal television display. In the conventional liquid crystal television, the number of scanning lines contained within the display is about 220 to 240 lines and the degree of resolution in the longitudinal direction across the screen is about one half of that of an ordinary television. Additionally, since all the scanning lines are scanned by a single field, the frequency for replacing data on the display is 60 Hz so that the display hardly exhibits flickering even when a liquid crystal display is utilized.
The small size liquid crystal video display has been satisfactory, however, the small size display suffers from lack of image quality and an inferior degree of resolution. Accordingly, large size liquid crystal video displays have been developed and various prototypes are known in the art. The larger the display the greater the number of picture elements required for that display. For example, in the convention large crystal displays, the number of scanning lines of the larger size liquid crystal display is from 440 to 480, twice as many as the number of scanning lines in the smaller size liquid crystal display described above.
The large size liquid crystal display suffers from the problem that when the liquid crystal display is driven in accordance with the interlace method as is done with a conventional television, the frequency for replacing data in the display is 30 Hz which results in flickering on the display. Therefore, it becomes necessary to scan the lines of an entire field through the non-interlace driving method so that the scanning speed is doubled and the frequency for replacing data on the display becomes 60 Hz limiting flickering. In the conventional large size liquid crystal display, the non-interlace driving method is utilized so that the video signals produced during a single horizontal signal period are displayed twice on two adjacent lines utilizing a line memory for storing the video signal during the period of a single horizontal signal. However, the conventional non-interlace driving method is unsatisfactory in that the same video data is displayed on two adjacent lines and therefore makes it difficult to take advantage of the larger display and improve the degree of vertical resolution. Accordingly, it is desirable to provide a video method display which overcomes the shortcomings of the prior art method described above.